Cutting matrix and method of applying the same

ABSTRACT

A method for applying cutting elements to a tool for cutting or milling a metal item in a well, along with the cutting element used in the method. The tool can include one or more blades extending outwardly or downwardly from the tool for cutting a metal item such as the wall of a casing string, or for removing a predetermined length of a casing string in a cutting action. The blade or blades have cutting elements positioned on the leading faces of the blades to engage the casing string or other metal item in the bore hole. Each cutting element is composed of a plurality of effective cutting faces. Each cutting face can have a substantially triangular shape, or a substantially square shape, or some other geometric shape. The cutting elements can be arranged in a random pattern. Each cutting element can be oriented in a random orientation relative to the blade. The cutting elements are shaped so that, regardless of the positioning or orientation of a given cutting element, it will continually present a sharp cutting edge to the metal object being cut. Each cutting face of each cutting element can also have one or more surface irregularities to cause the metal chips cut from the casings to break off at short lengths.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

This invention relates generally to a new method for applying aplurality of cutting edges to a tool for cutting or milling downholemetal items, such as fixed casing strings in a well bore, and to a newtype of cutting element used in this method.

Heretofore, cutting tools for cutting metal items downhole, such as wellcasing or casing strings, have been provided with one of two types ofcutting elements mounted on the cutting surfaces of the cutting tool.Generally, the two types of cutting elements which have been used are anaggregate of crushed tungsten carbide particles, or a pattern of wholecutting inserts. The cutting surfaces on which the aggregate or wholeinserts are mounted have been fixed blades, swinging blades, or the toolbody itself, depending upon the intended function of the tool.

Generally, the whole insert type of cutting element has been made ofcutting grade tungsten carbide, in the shape of discs, triangles,rectangles, parallelograms, or other shapes. These inserts have beenbonded to the cutting tool, sometimes in a uniform pattern, andsometimes in a random pattern. The random pattern is easier and moreeconomical to apply, but the uniform pattern has been more effective.Most of these whole inserts have had generally flat front faces, andgenerally flat rear faces, with the rear face being bonded to thecutting tool, and the front face being presented to the workpiece as acutting face. Most of these inserts also have substantially parallelfront and rear faces. One other known insert is a pyramid shape havingfour flat triangular sides.

It is important to cut relatively short, thick, metal chips from theworkpiece, to allow efficient removal of the chips from the well, viathe flow of drilling fluid. If this is not done, long, thin, stringymetal chips can be formed. These long, thin chips can adhere together,in a “bird nesting” effect, which can clog the drilling fluid flowpassages.

In order to promote the cutting of relatively short metal chips from theworkpiece with the whole cutting inserts, at least two types of featuressometimes have been employed. One such feature has been the provision ofa surface irregularity on the front face of each cutting insert, to curleach metal chip back toward the workpiece until it breaks off at arelatively short length.

The second such chip breaking feature has been to tilt the front face ofeach insert at a non-orthogonal attack angle relative to the surface ofthe workpiece. In this context, the term “rake angle” has been used torefer to the condition where one portion of the front face of the insertis advanced ahead of another portion, in the direction of rotation ofthe cutting tool. The degree of advancement is usually small, withapproximately 20° being the upper limit, resulting in an angle betweenthe front face of the cutting insert and the surface of the workpiece of70° to 90°. The rake angle can be “positive” or “negative”, dependingupon which portion of the front face of the cutting insert is advanced.If the leading portion of the front face contacts the workpiece surface,a “positive” rake angle is said to exist. If the trailing portion of thefront face contacts the workpiece surface, a “negative” rake angle issaid to exist. The use of a rake angle can cause the front face of theinsert to “drag” across the workpiece, or to “gouge” the workpiece,depending upon the particular type of rake angle employed, and dependingupon the contour of the cutting portion of the insert. A negative rakeangle is generally considered to achieve the best chip breaking effect.

The front face of the insert can have a “radial” rake angle, where thefront face lies in a plane which is parallel to the rotational axis ofthe cutting tool, but which extends non-radially from the cutting tool.Or, the front face of the insert can have an “axial” rake angle, wherethe front face lies in a plane which intersects, but does not contain,the rotational axis of the cutting tool. Or, the front face of theinsert can have a “compound” rake angle having both radial and axialcomponents.

A rake angle on the front face of the cutting insert can be the resultof an angle on the cutting tool surface on which the cutting insert ismounted, or an angle between the front face of the cutting insert andthe rear face, or both.

When tungsten carbide aggregate has been used as the cutting elementsinstead of whole cutting inserts, it has not been possible to employeither of the two chip breaking features discussed above. The tungstencarbide particles used as cutting elements in the aggregate are notuniform either in material or in conformation. They are typically madeby crushing whole inserts or worn out tungsten carbide machinecomponents, such as extrusion dies, rollers, or hammers. This produces awide assortment of shapes and sizes of particles, or chunks, of varyingformulations of tungsten carbide material. Some of these particles orchunks are not even “cutting grade” tungsten carbide, and some of thefaces or edge profiles of these particles or chunks are not suitable foruse on cutting elements. Even where surface irregularities are presenton the crushed carbide particles, they are not uniformly distributed oroptimally arranged on the front face of each cutting element, so theireffect is greatly reduced or eliminated.

The crushed aggregate is typically applied to the cutting tool in a moreor less random pattern, and each particle is randomly oriented on thesurface of the cutting tool. In one method, the crushed aggregate isformed into a solid bar by randomly suspending the particles in a matrixof brazing material, such as a nickel/brass matrix. The bar is thenbonded to the cutting tool as a unit. In another method, the crushedaggregate is randomly suspended within a welding rod and then bondeddirectly to the cutting tool, by melting of the welding rod onto thecutting tool. In either method, it is impossible to control theorientation of each particle of tungsten carbide relative to the cuttingtool. Therefore, it is impossible to control the angle at which theleading face or leading edge of each particle is ultimately presented tothe workpiece. Further, it is difficult to arrange the particles in auniform pattern on the cutting tool, since the particles are not ofuniform size and shape. Even though the technician typically attempts topack the crushed particles together for good coverage, some areas willhave a higher concentration of smaller carbide particles, with few openspaces therebetween, while other areas will have a lower concentrationof larger particles, with larger open spaces therebetween. Therefore, itis impossible to ensure that the various particles will achieve auniform cutting pattern on the workpiece. The result is a relativelyinefficient cutting tool.

The flat sided pyramid cutting insert is not particularly well suited tothis cutting tool application, because each pyramid insert will almostcertainly rest on one flat face, projecting a single point in thedirection of rotation of the cutting tool. In this orientation, thethree exposed flat side faces would be oriented at less than optimumangles for achieving the chip breaking effect.

Because of the relative inefficiency of the crushed tungsten carbideaggregate, the use of whole inserts arranged in a uniform pattern, withsome type of chip breaking feature being employed, has come to be theindustry standard for downhole milling and cutting. This efficiency hasa price, however, in that the arrangement of cutting inserts in auniform pattern, and the orientation of each insert at the optimumattack angle, add some expense and complexity to the cost ofmanufacturing the cutting tool. It is desirable to have a cuttingelement, and a method for applying cutting edges to a cutting tool,which will combine the simplicity of an aggregate cutting structure withthe cutting efficiency of a uniform pattern of uniformly orientedidentical cutting inserts.

BRIEF SUMMARY OF THE INVENTION

The present invention can be summarized as a cutting element for use ona tool for cutting or milling metal items downhole, and a method ofapplying such cutting elements to such cutting tools. The cuttingelements applied to a given cutting tool can be identically sized andshaped, and constructed of a uniform cutting grade material.Alternatively, a mixture of shapes can be employed, with each shapebeing designed to present an effective cutting contour to the workpiece.Each cutting element is composed completely of a plurality of faces,with each face having a basic geometric shape, such as an equilateraltriangle, or a square. All of the faces of a given element can beidentical. Throughout this application, the term “substantially” isused. In general, the term “substantially” should be understood to mean“essentially or completely, with only insignificant exceptions”. Morespecifically, the term is used herein to describe a cutting clementwhich is “substantially” formed of a plurality of faces, with each suchface having certain recited chip breaking characteristics. This meansthat all of the major faces are shaped to act as chip breakers. Therecould be very minor portions of the overall surface of the cuttingelement which are not thusly formed, but they are so minor that they donot alter the omnidirectional chip breaking function of the cuttingelement. Each face can be concave, in order to turn a metal chip backtoward the workpiece surface and break it off at a short length. Thecutting element can be cast of a high grade cutting formulation oftungsten carbide, or some other hard material. Alternatively, thecutting elements could conceivably be formed by other manufacturingprocesses. Each cutting element can have four, six, eight, or moreconcave faces. Each concave face of a cutting element can also have oneor more surface irregularities therein, to act as additional chipbreakers. These surface irregularities can be grooves, ridges, dimples,buttons, or other shapes capable of turning a metal chip back toward thesurface of the workpiece.

Each cutting element is shaped so that, regardless of which face isbonded to the cutting tool, and regardless of the angular orientation ofthe cutting element, an effective cutting edge will always be applied tothe workpiece. Each element is shaped so that it will have one of itsfaces bonded to the cutting tool, while the remainder of its faces areexposed. It does not matter which face is bonded to the cutting tool,because an arrangement of effective cutting faces will always be leftexposed. Furthermore, this arrangement of effective cutting faces isdesigned so that, regardless of the angular orientation of the cuttingelement, an effective cutting edge will always be presented to theworkpiece. Several shapes of cutting elements have been found to satisfythis requirement.

These cutting elements can be applied to the cutting tool in asubstantially random fashion, such as the methods for application of thecarbide particle aggregate discussed above, but the resulting pattern isfar more uniform with the cutting elements of the present invention.This is because the cutting elements of the present invention areuniform in size and shape, so when tightly packed together, they tend tocome to rest in a much more uniform pattern than would the variedassortment of crushed particles known in the prior art. Some of thecutting elements of the present invention are shaped such that severallayers of the elements can be applied, in a relatively uniform fashion.Further, when the cutting elements of the present invention are appliedto the cutting tool, the technician does not need to attempt to orientthe individual cutting elements in any particular way. The cuttingelements are designed so that, regardless of which face contacts thecutting tool, and regardless of how each cutting element is angularlyoriented, an effective cutting edge will always be applied to the workpiece.

The novel features of this invention, as well as the invention itself,will be best understood from the attached drawings, taken along with thefollowing description, in which similar reference characters refer tosimilar parts, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cutting element according to thepresent invention, having six identical square concave faces;

FIG. 2 is a perspective view of a cutting element according to thepresent invention, having faces with button for chip breakers;

FIG. 3 is a side elevation view of the element shown in FIG. 2;

FIG. 4 is a perspective view of a cutting element according to thepresent invention, having four identical triangular concave faces; and

FIG. 5 is a perspective view of a cutting element according to thepresent invention, having eight identical triangular concave faces.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a first embodiment 10 of the cutting element of thepresent invention has six identical faces 12. Each face 12 is concave,but its perimeter is substantially square. The concavity of each face 12makes it suitable for bending a metal chip back toward the workpiecesurface and breaking it off at a short length. The concavity of eachface 12 also establishes an effective attack angle relative to theworkpiece surface. Each face 12 is surrounded by four sharp, curved,cutting edges 14. Optionally, each face 12 can have an integral surfaceirregularity 16, which is shaped and located to aid in breaking offshort chips from the workpiece. The surface irregularity shown in eachface 12 in FIG. 1 is a groove with a rounded cross-section, but it couldalso be a ridge protruding from the face 12. Alternatively, the surfaceirregularities 16 could be dimples, buttons, or any other irregularitysuitable for turning a metal chip back toward the workpiece surface.Each of the four corners 18 of each face 12 can be sharp, as shown, orslightly rounded, without departing from the spirit of the presentinvention.

A plurality of the cutting elements 10 can be suspended in anickel/brass matrix, in a bar (not shown). Then, the bar can be bondedonto the cutting tool (not shown) in one piece, by a process such asbrazing. Similarly, a plurality of the cutting elements 10 can besuspended in a welding rod, and the welding rod can be melted onto thecutting tool. By either process, a plurality of the cutting elements 10will be deposited on, and bonded to, the cutting tool. Virtually all ofthe cutting elements 10 will come to rest on the cutting tool on one ofthe faces 12, with an axis A through this face 12 being essentiallyorthogonal to the surface of the cutting tool onto which the cuttingelement has been bonded. Since all of the cutting elements 10 areidentically sized and shaped, they will each present the same five-facedcontour protruding from the cutting tool. Since all of the cuttingelements 10 are identically sized and shaped, they will also easily packtogether in a relatively uniform pattern having a relatively constantdistribution of cutting elements 10 per square inch of cutting toolsurface. Because of the cubical shape of the cutting element 10, severallayers of the cutting element can be bonded to the cutting tool in arelatively uniform fashion.

Once a given cutting element 10 is positioned with one face 12 againstthe cutting tool, there is only one degree of freedom remaining, thatbeing the angular orientation about the axis A, as represented in FIG. 1by the arrow AO. Regardless of the final angular orientation AO of thecutting element 10, because of the uniformity of the six faces 12 andthe concavity of each face 12, an efficient cutting edge 14 or comer 18will be presented to the workpiece surface. The concavity of the face 12establishes a proper attack angle for cutting a metal chip from theworkpiece, breaking the chip off at a relatively short length.

The fact that each cutting element 10 constitutes an efficient cuttingelement, regardless of its positioning or orientation on the cuttingtool, enables the placement of a plurality of the cutting elements 10 onthe cutting tool in a substantially random fashion, such as the methodsdescribed above. Relatively rapid and economical placement of thecutting elements 10 is therefore possible, without detracting from thecutting efficiency of the resultant cutting tool.

A second embodiment 10′, shown in FIGS. 2 and 3, has six faces 12′. Eachface 12′ can be concave or flat, but its perimeter is substantiallysquare. One or more faces can be slightly larger or smaller than theremaining faces. Where concave faces are used, the concavity of eachface 12′ makes it suitable for bending a metal chip back toward theworkpiece surface and breaking it off at a short length. The concavityof each face 12′ also establishes an effective attack angle relative tothe workpiece surface. Each face 12′ is surrounded by four sharp,curved, cutting edges 14′. Optionally, either alternatively oradditionally, each face 12′ can have an integral surface irregularity16′, which is shaped and located to aid in breaking off short chips fromthe workpiece. The surface irregularities shown in each face 12′ inFIGS. 2 and 3 are buttons with rounded crosssections protruding from theface 12′, but they could also be dimples recessed into the face 12′.Alternatively, the surface irregularities 16′ could be grooves, ridges,or any other irregularity suitable for turning a metal chip back towardthe workpiece surface. Each of the four corners 18′ of each face 12′ canbe sharp, as shown, or slightly rounded, without departing from thespirit of the present invention.

A plurality of the cutting elements 10′ can be suspended in anickel/brass matrix, in a bar (not shown). Then, the bar can be bondedonto the cutting tool (not shown) in one piece, by a process such asbrazing. Similarly, a plurality of the cutting elements 10′ can besuspended in a welding rod, and the welding rod can be melted onto thecutting tool. By either process, a plurality of the cutting elements 10′will be deposited on, and bonded to, the cutting tool. Virtually all ofthe cutting elements 10′ will come to rest on the cutting tool on one ofthe faces 12′, with an axis A through this face 12′ being essentiallyorthogonal to the surface of the cutting tool onto which the cuttingelement has been bonded. All of the cutting elements 10′ are sized andshaped so that they will each present an effective five-faced cuttingcontour protruding from the cutting tool. Since the cutting elements 10′are similarly sized and shaped, they will also easily pack together in arelatively uniform pattern having a relatively constant distribution ofcutting elements 10′ per square inch of cutting tool surface. Because ofthe essentially cubical shape of the cutting element 10′, several layersof the cutting element can be bonded to the cutting tool in a relativelyuniform fashion.

Once a given cutting element 10′ is positioned with one face 12′ againstthe cutting tool, there is only one degree of freedom remaining, thatbeing the angular orientation about an axis, similar to the axis Arepresented in FIG. 1. Regardless of the final angular orientation AO ofthe cutting element 10′, because all of the six faces 12′ constituteeffective cutting contours, an efficient cutting edge 14′ or corner 18′will be presented to the workpiece surface. The concavity of the face12′ or the integrated chip breaker 16′ establishes a proper attack anglefor cutting a metal chip from the workpiece, breaking the chip off at arelatively short length.

The fact that each cutting element 10′ constitutes an efficient cuttingelement, regardless of its positioning or orientation on the cuttingtool, enables the placement of a plurality of the cutting elements 10′on the cutting tool in a substantially random fashion, such as themethods described above. Relatively rapid and economical placement ofthe cutting elements 10′ is therefore possible, without detracting fromthe cutting efficiency of the resultant cutting tool.

A third embodiment 20 of the cutting element of the present invention,shown in FIG. 4, has four identical faces 22. Each face 22 is concave,but its perimeter is substantially an equilateral triangle. Theconcavity of each face 22 makes it suitable for bending a metal chipback toward the workpiece surface and breaking it off at a short length.The concavity of each face 22 also establishes an effective attack anglerelative to the workpiece surface. Each face 22 is surrounded by threesharp, curved, cutting edges 24. Optionally, each face 22 can have anintegral surface irregularity (not shown) similar which is shaped andlocated to aid in breaking off short chips from the workpiece. Thesurface irregularity in each face 22 can be a groove, but it could alsobe a ridge protruding from the face 22. Alternatively, the surfaceirregularities could be dimples, buttons as shown in FIGS. 2 and 3, orany other irregularity suitable for turning a metal chip back toward theworkpiece surface. Each of the three comers 28 of each face 22 can besharp, as shown, or slightly rounded, without departing from the spiritof the present invention.

A plurality of the cutting elements 20 can be suspended in anickel/brass matrix, in a bar (not shown). Then, the bar can be bondedonto the cutting tool (not shown) in one piece, by a process such asbrazing. Similarly, a plurality of the cutting elements 20 can besuspended in a welding rod, and the welding rod can be melted onto thecutting tool. By either process, a plurality of the cutting elements 20will be deposited on, and bonded to, the cutting tool. Virtually all ofthe cutting elements 20 will come to rest on the cutting tool on one ofthe faces 22, with an axis A through this face 22 being essentiallyorthogonal to the surface of the cutting tool onto which the cuttingelement has been bonded. Since all of the cutting elements 20 areidentically sized and shaped, they will each present the samethree-faced contour protruding from the cutting tool. Since all of thecutting elements 20 are identically sized and shaped, they will alsoeasily pack together in a relatively uniform pattern having a relativelyconstant distribution of cutting elements 20 per square inch of cuttingtool surface.

Once a given cutting element 20 is positioned with one face 22 againstthe cutting tool, there is only one degree of freedom remaining, thatbeing the angular orientation about the axis A, as represented in FIG. 4by the arrow AO. Regardless of the final angular orientation AO of thecutting element 20, because of the uniformity of the four faces 22 andthe concavity of each face 22, an efficient cutting edge 24 or comer 28will be presented to the workpiece surface. The concavity of the face 22establishes a proper attack angle for cutting a metal chip from theworkpiece, breaking the chip off at a relatively short length.

The fact that each cutting element 20 constitutes an efficient cuttingelement, regardless of its positioning or orientation on the cuttingtool, enables the placement of a plurality of the cutting elements 20 onthe cutting tool in a substantially random fashion, such as the methodsdescribed above. Relatively rapid and economical placement of thecutting elements 20 is therefore possible, without detracting from thecutting efficiency of the resultant cutting tool.

A fourth embodiment 30 of the cutting element of the present invention,shown in FIG. 5, has eight identical faces 32. Each face 32 is concave,but its perimeter is substantially an equilateral triangle. Theconcavity of each face 32 makes it suitable for bending a metal chipback toward the workpiece surface and breaking it off at a short length.The concavity of each face 32 also establishes an effective attack anglerelative to the workpiece surface. Each face 32 is surrounded by threesharp, curved, cutting edges 34. Optionally, each face 32 can have anintegral surface irregularity (not shown) similar to the surfaceirregularity 16 in FIG. 1 or surface irregularity 16′ in FIGS. 2 and 3,which is shaped and located to aid in breaking off short chips from theworkpiece. The surface irregularity in each face 32 can be a groove, butit could also be a ridge protruding from the face 32. Alternatively, thesurface irregularities could be dimples, buttons as shown in FIGS. 2 and3, or any other irregularity suitable for turning a metal chip backtoward the workpiece surface. Each of the three corners 38 of each face32 can be sharp, as shown, or slightly rounded, without departing fromthe spirit of the present invention.

A plurality of the cutting elements 30 can be suspended in anickel/brass matrix, in a bar (not shown). Then, the bar can be bondedonto the cutting tool (not shown) in one piece, by a process such asbrazing. Similarly, a plurality of the cutting elements 30 can besuspended in a welding rod, and the welding rod can be melted onto thecutting tool. By either process, a plurality of the cutting elements 30will be deposited on, and bonded to, the cutting tool. Virtually all ofthe cutting elements 30 will come to rest on the cutting tool on one ofthe faces 32, with an axis A through this face 32 being essentiallyorthogonal to the surface of the cutting tool onto which the cuttingelement has been bonded. Since all of the cutting elements 30 areidentically sized and shaped, they will each present the sameseven-faced contour protruding from the cutting tool. Since all of thecutting elements 30 are identically sized and shaped, they will alsoeasily pack together in a relatively uniform pattern having a relativelyconstant distribution of cutting elements 30 per square inch of cuttingtool surface. Because each triangular face 32 of the cutting element 30has an opposite parallel triangular face 32, several layers of thecutting element 30 can be bonded to the cutting tool in a relativelyuniform fashion.

Once a given cutting element 30 is positioned with one face 32 againstthe cutting tool, there is only one degree of freedom remaining, thatbeing the angular orientation about the axis A, as represented in FIG. 5by the arrow AO. Regardless of the final angular orientation AO of thecutting element 30, because of the uniformity of the eight faces 32 andthe concavity of each face 32, an efficient cutting edge 34 or corner 38will be presented to the workpiece surface. The concavity of the face 32establishes a proper attack angle for cutting a metal chip from theworkpiece, breaking the chip off at a relatively short length.

The fact that each cutting element 30 constitutes an efficient cuttingelement, regardless of its positioning or orientation on the cuttingtool, enables the placement of a plurality of the cutting elements 30 onthe cutting tool in a substantially random fashion, such as the methodsdescribed above. Relatively rapid and economical placement of thecutting elements 30 is therefore possible, without detracting from thecutting efficiency of the resultant cutting tool.

While the particular invention as herein shown and disclosed in detailis fully capable of obtaining the objects and providing the advantageshereinbefore stated, it is to be understood that this disclosure ismerely illustrative of the presently preferred embodiments of theinvention and that no limitations are intended other than as describedin the appended claims.

I claim:
 1. A method for applying cutting elements to a tool for cuttingmetal in a well bore, said method comprising: providing a cutting tool;forming a plurality of cutting elements from a uniform material harderthan a piece of metal to be cut, with each said cutting element beingsubstantially formed of a plurality of cutting faces, with each saidface being shaped to turn a metal chip cut from a piece of metal backtoward the piece of metal being cut to break the chip off at a shortlength; and bonding a pattern of said plurality of cutting elements tosaid cutting tool.
 2. A method for applying cutting elements to acutting tool, as recited in claim 1, further comprising forming all saidcutting elements in identical shapes and sizes.
 3. A method for applyingcutting elements to a cutting tool, as recited in claim 1, furthercomprising forming all of said plurality of faces of a given cuttingelement in identical shapes and sizes.
 4. A method for applying cuttingelements to a cutting tool, as recited in claim 1, wherein at least onesaid face of at least one said cutting element is concave.
 5. A methodfor applying cutting elements to a cutting tool, as recited in claim 1,further comprising forming at least one chip breaking surfaceirregularity in at least one said face of at least one said cuttingelement.
 6. A method for applying cutting elements to a cutting tool, asrecited in claim 1, wherein at least one said face of at least one saidcutting element is substantially rectangular.
 7. A method for applyingcutting elements to a cutting tool for cutting metal in a well bore,said method comprising: providing a cutting tool; forming a plurality ofcutting elements from a uniform material harder than a piece of metal tobe cut, with each said cutting element being substantially formed of aplurality of cutting faces, with each said face being shaped to turn ametal chip cut from a piece of metal back toward the piece of metalbeing cut to break the chip off at a short length; and bonding a patternof said plurality of cutting elements to said cutting tool; wherein atleast one said face of at least one said cutting element issubstantially triangular.
 8. A method for applying cutting elements to acutting tool for cutting metal in a well bore, said method comprising:providing a cutting tool; forming a plurality of cutting elements from auniform material harder than a piece of metal to be cut, with each saidcutting element being substantially formed of a plurality of cuttingfaces, with each said face being shaped to turn a metal chip cut from apiece of metal back toward the piece of metal being cut to break thechip off at a short length; and bonding a pattern of said plurality ofcutting elements to said cutting tool; wherein at least one said face ofat least one said cutting element is substantially triangular; whereineach said cutting element is formed of four of said substantiallytriangular faces.
 9. A method for applying cutting elements to a cuttingtool for cutting metal in a well bore, said method comprising: providinga cutting tool; forming a plurality of cutting elements from a uniformmaterial harder than a piece of metal to be cut, with each said cuttingelement being substantially formed of a plurality of cutting faces, witheach said face being shaped to turn a metal chip cut from a piece ofmetal back toward the piece of metal being cut to break the chip off ata short length; and bonding a pattern of said plurality of cuttingelements to said cutting tool; wherein at least one said face of atleast one said cutting element is substantially triangular; wherein eachsaid cutting element is formed of eight of said substantially triangularfaces.
 10. A method for applying cutting elements to a cutting tool forcutting metal in a well bore, said method comprising: providing acutting tool; forming a plurality of cutting elements from a uniformmaterial harder than a piece of metal to be cut, with each said cuttingelement being substantially formed of a plurality of Cutting faces, witheach said face being shaped to turn a metal chip cut from a piece ofmetal back toward the piece of metal being cut to break the chip off ata short length; and bonding a pattern of said plurality of cuttingelements to a cutting tool; wherein each said cutting element is formedof six substantially rectangular faces.
 11. A method for applyingcutting elements to a cutting tool for cutting metal in a well bore,said method comprising: providing a cutting tool; forming a plurality ofcutting elements from a uniform material harder than a piece of metal tobe cut, with each said cutting element being substantially formed of aplurality of cutting faces, with each said face being shaped to turn ametal chip cut from a piece of metal back toward the piece of metalbeing cut to break the chip off at a short length; substantiallyrandomly placing each said cutting element within a pattern; and bondingsaid pattern of said plurality of cutting elements to a cutting tool.12. A method for applying cutting elements to a cutting tool for cuttingmetal in a well bore, said method comprising: providing a cutting tool;forming a plurality of cutting elements from a uniform material harderthan a piece of metal to be cut, with each said cutting element beingsubstantially formed of a plurality of cutting faces, with each saidface being shaped to turn a metal chip cut from a piece of metal backtoward the piece of metal being cut to break the chip off at a shortlength; substantially randomly orienting each said cutting elementrelative to said cutting tool; and bonding a pattern of said pluralityof cutting elements to a cutting tool.
 13. A method for applying cuttingelements to a tool for cutting metal in a well bore, said methodcomprising: providing a cutting tool; forming a plurality of identicallyshaped and sized cutting elements from a uniform material harder than apiece of metal to be cut, with each said cutting element being formed ofa plurality of identically shaped and sized contiguous faces; arrangingsaid plurality of cutting elements in a substantially random pattern onsaid cutting tool; orienting each said cutting element in asubstantially random fashion with respect to said cutting tool; andbonding said substantially random pattern of said substantially randomlyoriented plurality of cutting elements to said cutting tool.
 14. Amethod for applying cutting elements to a cutting tool, as recited inclaim 13, wherein each said face of each said cutting element isconcave.
 15. A method for applying cutting elements to a cutting tool,as recited in claim 13, further comprising forming at least one chipbreaking surface irregularity in each said face of each said cuttingelement.
 16. A cutting element for application to a tool for cuttingmetal in a well bore, said cutting element being substantially formedwith a plurality of cutting faces, with each said face being shaped toturn a metal chip cut from a piece of metal back toward the piece ofmetal being cut to break the chip off at a short length, and with saidcutting element being formed of a uniform material harder than the pieceof metal being cut.
 17. A cutting element as recited in claim 16,wherein all of said plurality of faces of said cutting element haveidentical shapes and sizes.
 18. A cutting element as recited in claim16, wherein at least one said face of said cutting element is concave.19. A cutting element as recited in claim 16, further comprising atleast one chip breaking surface irregularity formed in at least one saidface of said cutting element.
 20. A cutting element as recited in claim16, wherein each said face of said cutting element is substantiallyrectangular.
 21. A cutting element for application to a tool for cuttingmetal in a well bore, said cutting element being substantially formedwith a plurality of cutting faces, with each said face being shaped toturn a metal chip cut from a piece of metal back toward the piece ofmetal being cut to break the chip off at a short length, and with saidcutting element being formed of a uniform material harder than the pieceof metal being cut, wherein each said face of said cutting element issubstantially triangular.